[Computer-go] Chinese vs Tromp-Taylor rules

[Urban Hafner]

Hey Petr,

thanks for all the tips! There's still so much to do, which is quite a lot
of fun! ;)

Urban

On Fri, Mar 6, 2015 at 8:12 PM, Petr Baudis <pasky at ucw.cz> wrote:

> On Fri, Mar 06, 2015 at 10:25:14AM +0100, Urban Hafner wrote:
> > Now my question is what exactly do I have to do to implement chinese
> rules?
> > If I understand the differences correctly, the only difference between TT
> > and Chinese are (I somehow couldn't find any mention of positional super
> ko
> > in the TT rules on Senseis <http://senseis.xmp.net/?LogicalRules>, but
> IIRC
> > both use PSK):
> >
> > 1. Suicide isn't allowed in chinese rules
> > 2. Dead stones are removed before scoring in chinese
> >
> > Now #1 is simple and I've already implemented it as it's used by CGOS,
> but
> > how would I handle #2? I guess it needs to be a reasonably fast as it
> > should be used even in the playouts. It seems like a rather difficult and
> > error prone approach, or is there a quick way to find groups that are
> 100%
> > alive?
>
> (1) is correct.  (2) is too, but it is of course not mandatory; if you
> capture these stones, the score does not change even under Chinese
> rules, so you may just follow the same procedure as in TT rules.
>
> In the tree, to determine whether it's safe to pass and identify dead
> stones, a simple trick is to simply keep running statistics of average
> ownership of each point in final playout positions.  If it's the
> opponent's color 90% of time, you may assume it's dead.  (And this
> statistics can be useful for other purposes later too.)
>
> Ad superko, the rules say "(6) A turn is either a pass; or a move that
> doesn't repeat an earlier grid coloring." which is indeed positional
> superko, same as in Chinese rules.
>
> A pitfall to remember - in handicap games, handicap stones don't count
> in favor of black's score!
>
> > The alternative would be to continue using TT rules internally and just
> > play until there are only single point eyes left on the board.
>
> Thta's what Pachi does, and I believe many other programs too.
> We prevent multi-stone suicide only in the tree, not in playouts,
> for performance reasons (which might have became completely dubious
> meanwhile, though).
>
> --
>                                 Petr Baudis
>         If you do not work on an important problem, it's unlikely
>         you'll do important work.  -- R. Hamming
>         http://www.cs.virginia.edu/~robins/YouAndYourResearch.html
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